Sea to Summit Travelling Light Stuff Sack Set (S/M/L) Perfect for separating clothes and gadgets Made of strong, water resistant Ultra-Sil fabric Webbing loop for attaching to luggage or your body water-resistant products (such as the Ultra-Sil Stuff Sacks) are siliconized on both sides for ultimate packability waterproof products (such as the UltraSil Dry Sack are) siliconized on the outside and PU-coated on the inside to allow seam taping.